1. Technical Field
The invention pertains to a ventilating unit with moisture absorber, which is designed especially for motor vehicle headlights.
2. Discussion
Upon switching off the headlight, the air inside the headlight cools, so that its pressure decreases. As a result, a partial vacuum is produced within the headlight and outside air which may include moisture is sucked into the internal space of the headlight through its ventilation system, as well as within the body and lens of the headlight itself, so that condensation of the water vapor contained in the air drawn in may occur inside of the headlight.
In order to eliminate this problem, headlights are either provided with vent holes or they are equipped with elements containing silica gel for absorbing the water vapor from inside the headlight. Vent holes traditionally have limited effect on preventing condensation. An example of a solution with absorptive material is where a container for silica gel is placed outside the body of the headlight on its upper side, or a container in the shape of a horizontal letter T that contains absorptive material, is placed in a non-rear part of the body of the headlight. In the upper branch of the container is placed absorptive material with a vent tube and a drainage of condensate to the bottom part of the branch. Other examples that could be mentioned are the solutions contained in specifications GB 1472189 or FR 73.16520.
The drawback of the second solution is that the silica gel can only lower the relative humidity in the enclosed system to 40%, and after becoming saturated with water it has to be regenerated (dried out) by heating to 150° C.